KR100367377B1 - Method of Producing a Hydrogenation Catalyser - Google Patents

Abstract

A hydrogenation catalyst based on an alloy of aluminum and of a transition metal is prepared by preparing a kneaded material from the alloy and an assistant, converting the kneaded material into moldings, calcining the moldings and treating the calcined moldings with an alkali metal hydroxide, by a process in which the assistant used is (a) polyvinyl alcohol and water or (b) stearic acid, and the catalyst prepared according to the invention is used for hydrogenation and hydrogenolysis, in particular the partial hydrogenation of aliphatic alpha,omega-dinitriles to aliphatic alpha,omega-aminonitriles.

Description

Method of Producing a Hydrogenation Catalyser

The present invention is based on an alloy of aluminum and transition metals by preparing a kneaded product from an alloy and an auxiliary agent of aluminum and a transition metal, converting the kneaded product into a molding, calcining the molding and treating the calcined molding with an alkali metal hydroxide. The present invention relates to a method for producing a hydrogenation catalyst.

The invention furthermore relates to the use for hydrogenation and hydrogenolysis, in particular for the partial hydrogenation of aliphatic alpha, omega-dinitriles to aliphatic alpha, omega-aminonitriles and for the hydrogenation and hydrogenolysis of catalysts prepared according to the invention. It is about.

Ind. Eng. Chem. Res. 28 (1989), 1764-1767, describe a process for the preparation of Raney type catalysts. In this method, an alloy of aluminum and nickel is kneaded with polyethylene and mineral oil at 150 ° C. and extruded to obtain a molded product, and then the mineral oil is extracted with hexane. Thereafter, the molded product thus produced is calcined in an air at 900 to 1200 ° C., and some aluminum is oxidized to alumina. Treatment of the calcined molding with alkali metal hydroxide converts the molding into a catalyst and dissolves most of the unoxidized aluminum out of the molding. A disadvantage of this manufacturing method is that a relatively large amount (20% by weight) of mineral oil is used, and furthermore, this mineral oil has to be removed by further using hexane as an extractant in the process step before firing. In addition, the temperature of 150 ° C. during kneading is too high for commercial application, first of all due to energy consumption.

It is an object of the present invention to provide a method which does not have the above mentioned disadvantages. In particular, it is to provide a simplified process compared to the prior art, which does not require an intermediate step to remove the adjuvant.

The inventors believe that this object is achieved by preparing a blend with an alloy of aluminum and a transition metal and an adjuvant, converting the blend into a molding, firing the molding and treating the calcined molding with an alkali metal hydroxide. It has been found that this is achieved by an improved process for producing hydrogenation catalysts based on alloys of aluminum and transition metals, with (a) polyvinyl alcohol and water or (b) stearic acid as auxiliary aids.

In addition, the present inventors have found a method for hydrogenation and hydrogenolysis, in particular for aliphatic alpha, omega-dinitrile to aliphatic alpha, omega-aminonitrile, and for hydrogenation and hydrogenolysis of catalysts prepared according to the invention. Finally found use.

In the novel process of the present invention, the kneaded product is first prepared from an alloy of aluminum and a transition metal and an auxiliary agent.

Preferred transition metals include nickel, cobalt, iron and copper, and particularly preferably nickel and cobalt.

The aluminum alloy is produced by a method known per se, for example by the method described in German patent DE-A 21 59 736. The weight ratio of aluminum to transition metal in the alloy is generally selected from 35: 1 to 80: 1, preferably 50: 1 to 70: 1.

Adjuvants used according to the invention are (a) polyvinyl alcohol and water or (b) stearic acid.

Generally polyvinyl alcohols having a molecular weight of 3000 to 6000 g / mol, preferably 4500 to 5500 g / mol are used.

The weight ratio of polyvinyl alcohol to water is generally selected from 0.3: 1 to 0.4: 1, preferably 0.35: 1 to 0.37: 1. The observations thus far have found that, if possible, the kneaded material can be made into a hard-shell molding, if possible.

In a preferred embodiment, the alloy is first mixed with a generally solid polyvinyl alcohol and then water is added in small portions to produce an easily moldable and plastic kneaded product.

When using polyvinyl alcohol and water as an adjuvant, the weight ratio of the alloy to the adjuvant is generally selected from 4: 1 to 23: 1, preferably 13: 1 to 19: 1, and the preparation of the kneaded product is generally 10 to At 40 ° C., preferably 25-35 ° C.

The weight ratio of stearic acid to alloy is generally selected from 0.01: 1 to 1.0: 1, preferably 0.04: 1 to 0.06: 1, and the preparation of the kneaded product is generally 70 to 140 ° C., preferably 75 to 85 Generally at < RTI ID = 0.0 >

The kneaded product can be prepared by a method known per se, for example by a suitable mixing or kneading machine.

According to the invention, the moldings are made from kneaded products which are mainly composed of alloys and auxiliaries. The observations thus far have found that the three-dimensional shape of the moldings and their preparation is not critical to the success of the present invention. Preferred moldings are, for example, pellets and extrudates. Moldings are generally made in a device known for this purpose, for example by an extruder or pelletizer.

In the case of processing with an extruder, the L / D ratio is usually 10: 1 to 2: 1, preferably 3: 1 to 5: 1, the temperature is 10 to 40 ° C, preferably 25 to 35 ° C, and the pressure is 10 To 20 MPa, preferably 12.5 to 17.5 MPa.

In a particular embodiment, an extrudate having a diameter of 1.5 mm and a length of 5 mm is produced, wherein the production is generally performed immediately after exiting the extruder and the resulting extrudate is subjected to a temperature of 100 to 200 ° C. for surface drying. In a 0.2 to 2 minute treatment. It is then dried at 120 ° C. for 12 hours.

The moldings are usually calcined at 700 to 1200 ° C., preferably at 750 to 900 ° C., usually for a residence time of 0.5 to 3 hours, preferably 0.9 to 1.1 hours. In certain embodiments, the molding is first heated at 750 ° C. for 1 hour and then the temperature is raised to 900 ° C. for 2 hours.

Firing is generally carried out in an atmosphere at atmospheric pressure.

According to the invention, the calcined moldings are activated with alkali metal hydroxides or mixtures thereof, such as lithium hydroxide, sodium hydroxide, potassium hydroxide, or cesium hydroxide. Generally, aqueous alkali metal hydroxide solutions, in particular sodium hydroxide solutions, are water to alkali. The weight ratio of metal hydroxide is generally used in a range of 10: 1 to 30: 1, preferably 15: 1 to 25: 1. The molar ratio of alkali metal hydroxide to aluminum is generally selected from 1: 1 to 4: 1, preferably from 1.5: 1 to 2.5: 1. The activation temperature is generally selected from 25 to 95 ° C, preferably 45 to 80 ° C. The activation period depends essentially on the desired final aluminum content and is generally 10 to 30 hours, preferably 15 to 25 hours. Advantageously, activation is monitored by measuring the amount of hydrogen released during activation.

After activation, the activated and calcined molding is generally washed with water, preferably until the pH of the wash water is at least 8.0 and the molding is kept in water, preferably a mixture of water and methanol.

The catalysts prepared according to the invention are hydrogenated and hydrocracked, for example double and triple bonds of CC and CN, and hydrogenation of ketones and alcohols, ether splitting, reduction of nitro compounds and oximes, from ketones and primary amines. It can be used for the preparation of primary amines, dehalogenation and reduction of thioketones.

In a preferred embodiment, the catalyst according to the invention is used for partial hydrogenation of aliphatic alpha, omega-dinitrile to aliphatic alpha, omega-aminonitrile.

Partial hydrogenation can be carried out in the gas phase or in the liquid phase in a tube reactor by a liquid phase method or a trickle bed method, preferably a trickle bed method.

Aliphatic alpha, omega-dinitriles of formula (1) can be used as starting materials.

NC- (CH ₂ ) _n -CN

In the formula, n is an integer of 1 to 10, in particular 2, 3, 4, 5 or 6. Particularly preferred compounds of formula (1) include succinonitrile, glutaronitrile, adiponitrile, pimelonitrile and suberonitrile, more particularly preferably adiponitrile. In a preferred process, the dinitrile of formula (1) described above is partially hydrogenated using a catalyst prepared according to the invention in the presence of a solvent to obtain the alpha, omega-aminonitrile of formula (2).

NC- (CH ₂ ) _n -CH ₂ -NH ₂

In formula, n has the meaning mentioned above. Particularly preferred aminonitriles of formula (2) include compounds in which n is 2, 3, 4, 5 or 6, especially 4, ie 4-aminobutyronitrile, 5-aminopentanenitrile, 6-aminohexanenitrile (6 -Aminocapronitrile), 7-aminoheptanitrile and 8-aminooctanenitrile, more particularly preferably 6-aminocapronitrile.

Liquid partial hydrogenation is preferably carried out at 20 to 150 ° C., preferably at 30 to 90 ° C., and generally at 2 to 30 MPa, preferably at 3 to 20 MPa. Particularly preferably, partial hydrogenation is a solvent, preferably triamines having 1 to 6 carbon atoms, such as ammonia, amines, diamines and trimethylamines, triethylamine, tripropylamine or tributylamine, or methanol and ethanol And alcohols, particularly preferably in the presence of ammonia. In a preferred embodiment, 1 to 10, preferably 2 to 6 g of ammonia is selected per gram of adiponitrile. The catalyst space velocity is preferably selected from 0.1 to 2.0, preferably 0.3 to 1.0 kg of adiponitrile per liter per hour. In addition, the conversion rate and thus selectivity can be adjusted by changing the residence time.

In gas phase partial hydrogenation, it is generally maintained at a catalyst space velocity of 0.03 to 10, preferably 0.05 to 3 kg of dinitrile per kg of catalyst per hour.

The hydrogen concentration in the inlet gas generally depends on the dinitrile concentration. The molar ratio of hydrogen to dinitrile is generally 2: 1 to 300: 1, preferably 10: 1 to 200: 1.

The gas phase reaction can be carried out in the presence or absence of a solvent, for example, in a fixed bed reaction comprising a catalyst fixed by a liquid phase or trickle bed method, or continuously in a fluid bed reaction using a catalyst that flows up and down. The fixed bed method is preferred. By varying the residence time, the conversion and thus selectivity can be controlled.

In gas phase partial hydrogenation, the temperature is usually from 100 to 250 ° C., preferably from 150 to 220 ° C., in particular from 160 to 200 ° C., and the pressure is from 0.1 to 30 bar, preferably from 0.7 to 10 bar, particularly preferably from 0.9. To 5 bar is usually used.

In a preferred method, alpha, omega-aminonitrile is prepared using only a small amount of hexamethylenediamine with good selectivity. Moreover, the catalysts used according to the invention have a substantially longer lifetime than comparable prior art catalysts. Alpha, omega-aminonitrile is an important starting compound in the preparation of cyclic lactams, 6-aminocapronitrile for caprolactam.

An advantage of the novel process of the invention is that the process of the invention is simpler and less energy consuming than the process of the prior art.

<Example 1>

Preparation of Aluminum / Nickel Catalyst

Powder consisting of an alloy of 48% by weight of nickel and 52% by weight of aluminum (made similarly to Example 1 of German Patent DE-A 21 59 736) and 33 g of polyvinyl alcohol (molecular weight = 5000 g / mol) 90 ml of water was added little by little to the mixture, which was then kneaded with a kneader for 3 hours. The resultant kneaded was then treated with an extruder at 15 MPa and room temperature to obtain an extrudate with a thickness of 1.5 mm and a length of 5 mm. The resulting extrudate was surface dried at 120 ° C. for 2 hours and then held at 120 ° C. for 12 hours. Firing was first performed at 750 ° C. for 1 hour and then at 900 ° C. for 2 hours.

For activation, 1.5 l of a 20 wt% NaOH solution was added at 90 ° C. to 500 g of the extrudate thus prepared after the addition. After 26 hours (hydrogen production was 143.2 L), the extrudate was washed with water and the pH of the final wash water was 7.5.

<Example 2>

Preparation of Pellets Containing Stearic Acid as Adjuvant

2250 g of Al / Ni alloy powder (the powder used is the same as in Example 1) was heated to 80 ° C. and mixed with 112.5 g of liquid stearic acid. After cooling, the resulting solids were passed through a sieve having a mesh size of 1 mm to obtain a powder. This powder was pelletized with a pelletizer at room temperature (diameter: 3 mm, height 3 mm).

The pellets thus prepared were calcined at 900 ° C. for 2 hours. For activation, 1.5 L of 20 wt% sodium hydroxide solution was added to 411 g of pellet at 90 ° C. After 24 hours, the pellets were cooled and washed with water for 30 hours (the pH of the final wash water was 8.0).

<Example 3>

Partial hydrogenation

A mixture of 55 ml / h adiponitrile, 120 ml / h liquid ammonia, and 200 l / h hydrogen at 18 MPa and 35 ° C. was 55 cm in length, 1.5 cm in inner diameter, and 80 ml (156 catalysts prepared in Example 1) passed through a reactor containing g).

At a conversion of 56%, the reaction mixture consisted of 44% by weight of adiponitrile, 44% by weight of 6-aminocapronitrile and 12% by weight of hexamethylenediamine. When the temperature was increased to 40 ° C., the conversion increased to 68%. The reaction mixture consisted of 32% by weight of adiponitrile, 51% by weight of 6-aminocapronitrile and 17% by weight of hexamethylenediamine.

<Example 4>

Gas phase hydrogenation

Adiponitrile and hydrogen at a reaction temperature of 180 ° C. and a hydrogen / adipononitrile molar ratio of 50: 1 were passed through 100 ml of the catalyst obtained from Example 1 by a trickle bed method at a catalyst space velocity of ADN 0.15 g / g of catalyst / hour I was. The gaseous reacted mixture was condensed in a cold trap and analyzed by gas chromatography. The yield of 6-amino-capronitrile was 53% (72% selectivity, 74% conversion) and the yield of HMD was 6%.

Claims (9)

Preparing a kneaded material from an alloy of aluminum and a transition metal and (a) polyvinyl alcohol and water or (b) a stearic acid adjuvant, converting the kneaded material into a molding, calcining the molding and calcined molding A process for producing a hydrogenation catalyst based on an alloy of aluminum and transition metal by treating with alkali metal hydroxide. The method of claim 1 wherein nickel, cobalt, iron or copper is used as the transition metal. The process according to claim 1 or 2, wherein the kneaded product is prepared at 70 to 140 ° C. The method of claim 1 or 2, wherein the adjuvant is not removed before firing. The method of claim 1 or 2, wherein the weight ratio of polyvinyl alcohol to water is selected from 0.3: 1 to 0.4: 1. The method of claim 1 or 2, wherein the weight ratio of alloy to polyvinyl alcohol is selected from 20: 1 to 80: 1. The process according to claim 1 or 2, wherein the polyvinyl alcohol has a molecular weight of 3000 to 6000 g / mol. Process for hydrogenation and hydrogenolysis in a manner known per se, using a catalyst prepared by the method of any one of claims 1-7. In the process for producing aliphatic alpha, omega-aminonitrile by partially hydrogenating aliphatic alpha, omega-dinitrile at elevated temperature in the presence of a solvent and a catalyst, the hydrogenation catalyst used is based on an alloy of aluminum and transition metal, Preparing a kneaded product from this alloy and (a) a polyvinyl alcohol and an adjuvant that is (b) stearic acid, converting the kneaded material to a molding, calcining the molding and finally the calcined molding to an alkali metal The process obtained by treating with a hydroxide.